ISSN NUMBER: 1938-7172
Issue 4.4 VOLUME 4 | NUMBER 4

Editor:
Michael A. Fiedler, PhD, CRNA

Contributing Editors:
Penelope S. Benedik PhD, CRNA, RRT
Joseph F. Burkard, DNSc, CRNA
Mary A. Golinski, PhD, CRNA
Gerard T. Hogan, Jr., DNSc., CRNA
Alfred E. Lupien, PhD, CRNA
Lisa Osborne, PhD, CRNA
Dennis Spence, PhD, CRNA
Steven R. Wooden, MS, CRNA

Guest Editors:
Sandra L. Larson, PhD, CRNA, APN
Cassandra Taylor, DNP, DMP, CRNA, CNE

Assistant Editor
Jessica Floyd, BS

A Publication of Lifelong Learning, LLC © Copyright 2010

New health information becomes available constantly. While we strive to provide accurate information, factual and typographical errors may occur. The authors, editors, publisher, and Lifelong Learning, LLC is/are not responsible for any errors or omissions in the information presented. We endeavor to provide accurate information helpful in your clinical practice. Remember, though, that there is a lot of information out there and we are only presenting some of it here. Also, the comments of contributors represent their personal views, colored by their knowledge, understanding, experience, and judgment which may differ from yours. Their comments are written without knowing details of the clinical situation in which you may apply the information. In the end, your clinical decisions should be based upon your best judgment for each specific patient situation. We do not accept responsibility for clinical decisions or outcomes.

Table of Contents

AIRWAY
  LARYNGEAL MASK AIRWAY OR ENDOTRACHEAL TUBE FOR PERCUTANEOUS DILATION TRACHEOSTOMY: A COMPARISON OF VISIBILITY OF INTRATRACHEAL STRUCTURES
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CARDIOVASCULAR
  IMPAIRED AUTOREGULATION OF CEREBRAL BLOOD FLOW DURING REWARMING FROM HYPOTHERMIC CARDIOPULMONARY BYPASS AND ITS POTENTIAL ASSOCIATION WITH STROKE.
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OBSTETRIC ANESTHESIA
INCIDENCE AND RISK FACTORS OF AMNIOTIC-FLUID EMBOLISM
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PHARMACOLOGY
MONITORED ANESTHESIA CARE (MAC) SEDATION: CLINICAL UTILITY OF FOSPROPOFOL
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INCIDENCE OF SEDATION-RELATED COMPLICATIONS WITH PROPOFOL USE DURING ADVANCED ENDOSCOPIC SURGICAL PROCEDURES
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THE EFFECT OF PREOPERATIVE HEART RATE AND ANXIETY ON THE PROPOFOL DOSE REQUIRED FOR LOSS OF CONSCIOUSNESS
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POLICY, PROCESS, & ECONOMICS
MAXIMAL STERILE BARRIER PRECAUTIONS DO NOT REDUCE CATHETER-RELATED BLOOD STREAM INFECTIONS IN GENERAL SURGERY UNITS
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QUALITY IMPROVEMENT
POSTOPERATIVE PATIENT COMPLAINTS: A PROSPECTIVE INTERVIEW STUDY OF 12,276 PATIENTS
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Attention subscribers licensed in Alabama, Alaska, Idaho, Kentucky, Nevada, and New Mexico: This issue contains 1 PHARMACOLOGY specific CE credit.


Airway

Linstedt U, Zenz M, Krull K, H?gar D, Prengel AW


 

Laryngeal mask airway or endotracheal tube for percutaneous dilation tracheostomy: a comparison of visibility of intratracheal structures

Anesth Analg 2010;110:1076-82

Linstedt U, Zenz M, Krull K, Hägar D, Prengel AW

 

 

Abstract

Purpose            The purpose of this study was to compare differences in visibility of intratracheal structures with laryngeal mask airway (LMA) or endotracheal tubes (ETT) during percutaneous dilatational tracheostomy (PDT).

Background            PTD is a common procedure to facilitate long-term ventilation in critically ill patients. However, complications such as damage to the tracheal wall, ETT cuff rupture, or accidental extubation with subsequent hypoxia can occur with PDT, especially with insufficient visualization of intratracheal structures. Bronchoscopy through an existing ETT is the most common method used to identify intratracheal structures; however ETT may not always provide the best visualization of airway structures. At the investigators institution, intensivists prefered LMA for airway management during PDT because they improve visualization of intratracheal structures. Previous studies have not compared visualization of intratracheal structures during PDT.

Methodology            This was a prospective, randomized, controlled trial comparing visualization of intratracheal structures during PDT with LMA or ETT. All subjects were ICU patients requiring tracheostomy for long-term ventilation. Subjects with difficult airways, PaO2/FiO2 <200 and PEEP ≥ 15 mmHg were excluded. Sedation was maintained with sufentanil and midazolam infusions and muscle relaxation with cisatracurium. Propofol was administered as needed. All PDTs were performed by intensivists with at least 10 PDTs (range 10-200 PDTs).

Subjects in the LMA group had an LMA Classic™ introduced behind an in situ ETT. Once the LMA was placed the ETT was removed. In the ETT group the existing tube was used. All subjects received positive pressure ventilation with FiO2 1.0. A video bronchoscope was introduced through either device and the PDT was performed. The primary outcome was quality of visualization of intratracheal structures (thyroid, cricoid, and 1st to 3rd tracheal cartilages) as measured by the intensivist on a 4 point likert scale (1-very good, 2-good, 3-difficult, and 4-not possible). A rating of 4 required an alternative airway. Secondary outcomes included monitoring of the puncture of the trachea and of the dilation process. Additional outcomes included quality of ventilation and complications.

Result            The completed study included data from 63 subjects (LMA n = 33, ETT n = 30). No differences were noted between the groups in baseline demographics or hemodynamics during the procedure. Visualization of tracheal structures was significantly better in the LMA group, with 94% of subjects compared to 66% of subjects in the ETT group having very good or good visualization (P < 0.05). In one subject in the LMA group the bronchoscope was difficult to guide through the vocal cords (rating 3). In 10 subjects in the ETT group relevant structures could not be identified compared to 1 in the LMA group (P < 0.01). Monitoring of tracheal puncture was rated as very good or good in 97% of subjects compared to 77% in the ETT group (P <0.05). Poor visualization of tracheal structures occurred in 5 subjects in the ETT group during puncture and dilation (P < 0.01). Blood gas analysis revealed significantly higher PaCO2 before puncture of the trachea in the ETT group (59 ± 14 vs. 51 ± 11, P = 0.01).

Five patients had ratings of 4 (difficult) and severe complications during PDT. In the ETT group 1 subject was accidentally extubated, 1 was unable to be ventilated after tracheal puncture, and in 1 subject no adequate position for bronchoscopy could be found. In 1 subject in the LMA group insertion of the LMA was not possible.

Conclusion            Visualization of tracheal structures during PTD was much better with an LMA than an ETT.

 

Comment

I found this study to be interesting because I have never used an LMA for a PDT or standard tracheostomy, but after reading this article I think it is another tool that anesthesia providers should keep in their tool bag. The problem I have always had when using an ETT for this procedure is that the patient gets accidentally extubated, or the pilot balloon is ruptured, and/or it is difficult to oxygenate and ventilate the patient once the trachea is punctured. Using an LMA might mitigate some of these problems, and from the results presented in this study, it appears to improve visualization of the structures, which appears to be critical to the success of the procedure.

There are however, several limitations and weaknesses in this study. First, the authors did not list how many intensivists were involved in the study. From the data presented it appears there was a wide range of experience level (10 to 200 PDTs). Another issue is that it appears that at this facility they have been using LMAs for PDTs for some time, and that the intensivists prefer the LMA over the ETT because it improves the visualization. It may be that the intensivists, especially junior intensivists, who were performing the procedure and rating the visualization of structures, may have been more proficient with using an LMA than an ETT for PDT because that is how they learned to do the procedure. This is not unlike what I have seen with axillary nerve blocks, where many new anesthesia providers at my facility are trained to do the block under ultrasound rather than straight nerve stimulation, thus are less proficient with the latter.

Having said that I still think the findings are pertinent to anesthesia providers. Something new I learned from the article was that it is possible to insert an LMA behind an ETT, which can then be removed once the LMA is in the correct position. This technique might prove useful in situations such as PDT, or maybe at the end of a thyriodectomy when you want to evaluate vocal cord function, which could be easily accomplished by passing a bronchoscope through an LMA.

Dennis Spence, PhD, CRNA

 

The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, Department of Defense or the United States Government.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010




Cardiovascular

Joshi B, Brady K, Lee J, Easley B, Panigrahi R, Smielewski P, Czosnyka P, Hogue, Jr. CW


 

Impaired autoregulation of cerebral blood flow during rewarming from hypothermic cardiopulmonary bypass and its potential association with stroke.

Anesth Analg 2010;110:321-328

Joshi B, Brady K, Lee J, Easley B, Panigrahi R, Smielewski P, Czosnyka P, Hogue, Jr. CW

 

 

Abstract

Purpose            The purpose of this study was to evaluate cerebral blood flow velocity and autoregulation during hypothermic and normothermic cardiopulmonary bypass in adult patients.

Background            This study evaluated whether or not cooling and rewarming of body temperature in adult patients during cardiopulmonary bypass (CPB) was associated with alterations in cerebral blood flow (CBF) autoregulation.

Methodology            One hundred twenty seven adult patients undergoing CPB with hypothermia and rewarming were evaluated for changes in CBF autoregulation using transcranial doppler blood flow velocity measurements in the left and right middle cerebral arteries. Eleven adult patients undergoing CPB without hypothermia served as controls. The researchers considered a transcranial doppler blood flow velocity : mean arterial pressure correlation value of 0.0 to reflect normal CBF autoregulation. A correlation  > 0.4 was considered positive for impaired CBF autoregulation, and indicative of cerebral flow velocity changes directly correlating with changes in mean arterial pressure.

Result            CBF autoregulation was impaired in 43% of patients during the cooling phase of CPB, and in 68% of the patients during the rewarming phase. However, CBF autoregulation was also impaired in nine of the eleven control patients (82%) during the entire period of CPB. Seven patients developed strokes and one patient developed a transient ischemic attack. Neurologic events occurred exclusively in patients who underwent hypothermic CPB, and who also demonstrated impaired autoregulation.

Conclusion            Hypothermic CPB was associated with abnormal CBF autoregulation, which became impaired during cooling and worsened during rewarming. Whether or not impaired CBF autoregulation increased the risk for ischemic brain injury needs further investigation.

 

Comment

This study provided NO basis for changing the standard practice of cooling and rewarming adult patients during CPB. Despite the finding that impaired CBF autoregulation occured in a majority of patients during cooling and rewarming, the research DID NOT show that impaired CBF autoregulation was the result of cooling and rewarming. This was because the research methods did not control for known confounding variables affecting CBF autoregulation. And, because the patients who were not cooled and rewarmed also demonstrated a similar degree of impaired CBF autoregulation, but with a higher incidence!

This study provided NO insight into the affect of impaired CBF autoregulation on neurological outcome in cardiac surgery patients. While neurological events occurred exclusively in patients who were cooled and rewarmed and who also demonstrated impaired CBF autoregulation, the research methods precluded ones ability to draw conclusions from this finding. This is because the sample size is too small, stroke types were not differentiated, and the research did not consider confounding variables affecting stroke risk. For example, no patients in the control group had valve surgical procedures, yet 40% of the patients who were cooled and rewarmed had valve surgical procedures. In addition, the control group had a shorter duration on CPB, and shorter duration of aortic cross clamping. These three variables are known risk factors for stroke during cardiac surgery (1), and may explain why strokes were not seen in control group patients, even though they also demonstrated impaired CBF autoregulation.

This study is important for its ability to demonstrate a mechanism for evaluating CBF autoregulation.

 

Sandra L. Larson, PhD, CRNA, APN

 

Bucerius J, Gummert JF, Borger MA, Walther T, Doll N, Onnasch JF, et al. Stroke after cardiac surgery: a risk factor analysis of 16,184 consecutive adult patients. Ann Thorac Surg. 2003;75:472-478.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010




Obstetric Anesthesia

Knight M, Tuffnell D, Brocklehurst P, Spark P, Kurinczuk K


 

 

Incidence and risk factors of amniotic-fluid embolism

Obstet Gynecol 2010;115:910-7

Knight M, Tuffnell D, Brocklehurst P, Spark P, Kurinczuk K

 

 

Abstract

Purpose            The purpose of this study was to determine the incidence, risk factors, management, and outcomes of amniotic-fluid embolism (AFE).

Background            AFE is a leading cause of maternal mortality. The United States and Australia have reported an increase in the number of deaths from AFE. However, because the disorder is so rare it is unclear if the increase in deaths is due to an increase in the condition or a chance finding. In the United Kingdom there is a prospective reporting system which tracks cases through the UK Obstetric Surveillance System.

Methodology            This was a prospective, population-based cohort and nested case-control design analyzing cases of AFE from the UK Obstetric Surveillance System between February 2005 and February 2009. The diagnostic criteria for AFE are listed in Table 1:

Table 1. Amniotic-fluid Embolism Diagnostic Criteria

Acute maternal collapse without another cause, with one or more of the following features:

     Acute fetal compromise

     Cardiac arrest

     Cardiac arrhythmias

     Coagulopathy

     Hypotension

    Early symptoms: e.g., restlessness, numbness, agitation, tingling

     Seizures

     Shortness of breath

Exclude primary maternal hemorrhage without evidence of early coagulopathy or cardio-pulmonary compromise

Postmortem examination revealing fetal squamous cells or hair in maternal lungs

 

Logistic regression was used to estimate the odds ratio and determine risk factors and confounding variables of AFE. A nested control group of 1,227 parturients was used to compare results. The proportion of cases (e.g., AFE) related to specific causes (i.e., induction of labor) were presented as population-proportional attributable risks.

Result            The incidence of AFE was 2 per 100,000 deliveries (60 cases out of 3,049,000 deliveries at 229 UK hospitals). Older women (>35 years old) and ethnic minority women were 9.85 times more likely to have an AFE (95% CI 3.57-27.2), and to die from it. The majority of women (n = 55, 92%) with AFE had ruptured membranes at or before symptoms presented. Twenty-six women developed symptoms after delivery, with 19 of 26 (73%) occurring after cesarean delivery. Twelve women (20%) died from AFE, with the median time to death being 1 hour and 40 minutes after the event (range 0 minutes to 23 hours, 18 minutes).

Induction of labor increased the odds of an amniotic-fluid embolism by 3.86 times (95% CI 2.04-7.31). Women with multiple gestations were 10.9 times (95% CI 2.81-42.7) likely to suffer an AFE, as were women who required a cesarean delivery (odds ratio 8.84, 95% CI 3.70-21.1). The population population-attributable risk for induction of labor was 35%, which suggests if labor was no longer induced that 35% of cases of amniotic-fluid embolism could be prevented. Likewise, the population-attributable risk for ethnic minority women >35 y/o was 13%, 7% for multiple gestation, and 62% for cesarean delivery, respectively.

The most common first signs or symptoms of AFE were restlessness, agitation, or numbness (n = 18, 30%), shortness of breath (n = 12, 20%) or acute fetal compromise (n = 12, 20%). Other common features (some women experienced more than one) included: hemorrhage (n = 39; 62%), hypotension (n =38; 63%), acute fetal compromise (n = 26; 43%), and cardiac arrest (n = 24, 40%).

A total of 12 out of 60 (20%) women died from AFE, with a majority of them dying before admission to the intensive care unit (n = 9; 75%). Of those women who survived (n = 48), supportive therapies were the most common treatment (n = 26; 54%). Other common management techniques included hysterectomy (n = 12; 25%), and factor VIIa administration (n = 14; 29%).

Conclusion            High-quality supportive care can lead to good outcomes after AFE. More restricted use of induction of labor and cesarean delivery may help decrease the incidence of AFE. Increased mortality in ethnic minority women may be related to less access to medical care and/or underlying comorbidities.

Comment

I am always impressed with the ability of researchers in the United Kingdom to conduct high quality epidemiological studies on rare conditions such as amniotic-fluid embolism. This was a good prospective study which demonstrates that AFE is truly a rare event, with a mortality rate of 20%. I suspect this lower than expected mortality rate is due to prompt identification and treatment, albeit supportive, of AFE.

I think the most important take home point for anesthesia providers from this study are the common signs and symptoms of AFE. Just a few weeks ago I was speaking with an Obstetrician I work with and he described a patient he took care of who had this feeling of “impending doom” right before she experienced an AFE. I think this highlights what the authors found in that 30% of women experienced very similar initial symptoms (i.e., restlessness, agitation, numbness, tingling). Therefore I think if a parturient describes these signs and symptoms anesthesia providers should not discount them, and be prepared to  assist with resuscitation (i.e., ACLS, airway management) if an AFE develops.

  

Dennis Spence, PhD, CRNA

 

1. Natarajan S, Lipsitz SR, Rimm E. A simple method of determining confidence intervals for population attributable risk from complex surveys. Statistics in Medicine.2007;26(17):3229-39.

 

Population-proportional attributable risk combines information on prevalence and a measure of association to provide an estimate of the proportion of disease in the population that is directly attributable to a particular risk factor.1 From a public health perspective, population-proportional attributable risk can be used to calculate the proportion of a disease that could be prevented if exposure to an event were eliminated. For example, in this study induction of labor was associated with a population-attributable risk of 35%, which suggests if labor was no longer induced that 35% of cases of amniotic-fluid embolism could be prevented. A premise behind this measure is that it assumes causality.

 

The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, Uniformed Services University of the Health Sciences, Department of Defense or the United States Government.

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010




Pharmacology

Harris E, Lubarsky D, Candiotti K


 

Monitored Anesthesia Care (MAC) Sedation: clinical utility of fospropofol

Ther Clin Risk Manag 2009;5:949-959

Harris E, Lubarsky D, Candiotti K

 

 

Abstract

Purpose            This article reviewed research findings, pharmacokinetics, and pharmacodynamics of fospropofol.

Background            Moderate sedation is a concept that includes the maintenance of a patent airway, stable cardiovascular and respiratory systems, and a consciousness level responsive to verbal or light tactile stimulation. Propofol, a short acting anesthetic agent introduced in 1986, is thought to be the predominant agent used for moderate sedation. It provides a quick recovery time, a low incidence of nausea, and has a high degree of satisfaction among patients. It has been associated with cardiovascular and respiratory depression, and therefore should be used only by health care providers capable of managing those potential side effects. Gastroenterologists disagree with the FDAs recommendation that propofol should only be used by anesthesia providers. They argue that this recommendation is unnecessary and only adds an additional layer of cost to a procedure. As an example, colonoscopies using an anesthesia provider add between $250 and $400 to the procedure. Anesthesia providers on the other hand argue that propofol has a very narrow therapeutic range and a patient can slip from moderate sedation to general anesthesia unexpectedly. For that reason, it is argued, an anesthesia provider is necessary when propofol is used for sedation. This argument set the stage for the development and marketing of a milder form of propofol.

Method            Propofol phosphate, later called fospropofol, is a water soluble prodrug which reliably produces sedation. It does so by undergoing hydrolysis by alkaline phosphatase to release the active metabolite propofol. Formaldehyde and phosphate are also released, but the formaldehyde is converted to a less toxic substance called formate. The pharmacodynamic properties appear to be different between fospropofol and propofol. Fospropofol is reported to have a smaller volume of distribution, higher peak plasma concentrations, and a shorter half life because of more rapid clearance. The byproduct of fospropofol, formate, can cause acidosis, ketonemia, acetonuria, respiratory compromise and blindness in high concentration. However, controlled studies have shown no significant difference in formate concentrations between subjects receiving fospropofol and those who receive propofol.

Results            Controlled studies have shown fospropofol to have a wide therapeutic range. In one small study of nine subjects, three groups of adult volunteers received an intravenous infusion of fospropofol over a ten minute period of time in doses of 290 mg, 580 mg, and 1160 mg respectively. No member of the 290 mg group lost consciousness. One member of the 580 mg group lost consciousness for 10 minutes. In the highest dose group, all patients lost consciousness for 9 to 12 minutes after the start of the infusion and remained unconscious, spontaneously breathing, and maintained an oxygen saturation of 93% or above throughout the 24 to 26 minutes of unconsciousness. In addition, the subjects displayed a slight elevation in blood pressure and pulse. All nine volunteers reported itching, burning, and paresthesia in the anal and genital regions. In 2005, a group of 36 volunteers were given boluses of fospropofol and propofol between 5 mg and 30 mg per kilogram. The fospropofol group all displayed initial small increases in blood pressure and pulse followed by a gradual decline in both to 20-25% of baseline. The propofol group typically showed no increase in blood pressure or pulse initially, followed by a more dramatic drop in blood pressure to 20% of baseline. All subjects in the fospropofol group reported paresthesia in the genital area. Both groups receiving fospropofol and propofol displayed a statistically similar time to loss of consciousness. Fospropofol and propofol were both easily titrated to produce various levels of consciousness, but fospropofol recovery was on average 10 minutes longer than propofol after a 2 hour infusion. Adverse events reported in both groups were pruritus, hypotension, and oxygen desaturation.

Conclusion            Clinical studies suggest that fospropofol may be as efficacious as propofol for sedation during minor diagnostic procedures. One study suggests that in the time it takes to complete one colonoscopy using midazolam and meperidine, almost 2 colonoscopies can be completed using fospropofol because of the rapid induction and recovery rates of fospropofol compared to midazolam and meperidine. Although fospropofol is not intended to be an induction agent, it may still produce unintended general anesthesia, aspiration, and cardiopulmonary compromise. Because of those risks, the authors of this article believed that fospropofol use should be limited to those practitioners trained in the administration of anesthesia. Apparently the FDA agrees. It is likely that fospropofol will be a useful adjunct for anesthesia providers administering monitored anesthesia care.

 

Comment

Fospropofol is sold under the brand name Lusedra. It originally was named Aquavan, but the patent was bought by another corporation that decided to market it under the new name. I have not had the opportunity to use the drug, and I will gladly try it out for moderate sedation, but I am not yet convinced that the literature has shown it to provide any significant benefits over propofol. In some studies, fospropofol has actually shown a longer recovery time than propofol. The annoying side effect of anal itching is disconcerting, and the clinical trials indicate that the possibility of respiratory depression still exists. This may be a case of a new drug, with better profit margins, being marketed to replace an older drug that has outlived its profit potential. Perhaps it will show improved use and outcomes, but only time will tell. In the mean time, as I get older and wiser, I find myself less attracted to advertisement, and more interested in clinical studies. No matter what the advertisement says, the clinical studies have yet to show me that fospropofol is a vast improvement over propofol. Even better, I can cut my propofol use in half by using midazolam and then reversing the midazolam with flumazenil at the end of the case. I will suggest that my colonoscopy patients are comfortable, recover faster, and have fewer side effects than propofol or fospropofol alone. I think I have just found a wonderful clinical study to conduct.

 

Stevn R. Wooden, MS, CRNA

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010





Cot? GA, Hovis RM, Ansstas MA, et al.


 

Incidence of sedation-related complications with propofol use during advanced endoscopic surgical procedures

Clin Gastroenterol Hepatol 2010;8:137-42

Coté GA, Hovis RM, Ansstas MA, et al.

 

Abstract

Purpose            The purpose of this study was to evaluate the incidence and independent predictors of the need for airway intervention during propofol administered by CRNAs during advanced endoscopy procedures.

Background            Propofol is a popular agent for endoscopic procedures because of its fast onset and short duration of action. A few studies in the Gastroenterology literature suggest that propofol can safely be administered by non-anesthesia providers (i.e., gastroenterologist-supervised RN administered propofol) for routine endoscopy procedures (i.e., colonoscopy and endoscopic gastroduodnoscopy), as well as advanced endoscopy procedures such as endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound (EUS) in patients at low risk for cardiopulmonary complications. However, personnel administering these drugs should be able to rescue patients from general anesthesia and/or respiratory depression.

Methodology            This prospective study evaluated the frequency of sedation-related adverse events and predictors of the need for one or more airway interventions during advanced endoscopy procedures at a major university hospital between May 2008 and November 2008. Sedation was provided by three CRNAs with extensive experience providing sedation for these procedures. Deep sedation was provided with propofol alone or in combination with a small amount of opioids and/or benzodiazepines. Outcomes of the study are listed in Table 1:

 

Table 1. Outcomes and definitions

Primary

Frequency of sedation-related adverse events

     Hypoxemia: SPO2 < 90% of any duration

     Hypotension: SBP < 90 mm Hg requiring use of vasopressors

     Need to terminate procedure for issues related to sedation

Need for one or more airway interventions

Secondary

     Independent predictors of need for airway interventions (Intervention + or Intervension –)

     Evaluation of procedural and pharmacological data for patients who received propofol alone

      vs. propofol combination (propofol + opioids and/or benzodiazapines)

Note. Airway interventions (Intervension +) were defined as a chin lift, nasopharyngeal airway, modified mask airway, bag-valve mask ventilation, or endotracheal intubation.

 

Descriptive statistics and logistic regression (need for Airway Intervention yes or no) were used to analyze the primary and secondary outcomes, respectively.

Result            A total of 799 patients were enrolled; 423 (52.9%) EUSs, 336 (42.1%) ERCPs, and 40 small-bowel enteroscopy procedures were performed over 7-months. Subjects mean age was 58 ± 16.5 years, with 47% being male and 61% being ASA ≥ 3, respectively. Mean BMI was 27 ± 6.5 kg/m2. Procedures took an average of 30 ± 18.8 minutes, with approximately one-third (37%) being performed in the prone position (i.e., ERCPs). A large portion of patients had no response to endoscope insertion (87%). For induction, 61% received a combination of propofol (mean dose: 1.79 ± 1.06 mg/kg) and opioid and/or benzodiazepine. Total propofol dose and infusion duration was 0.19  ± 0.11 mg/kg/min and 34.4 ± 18.8 min, respectively. Median Aldrete score was 9 after the procedure.

The most common sedation-related adverse event was hypoxemia (12.8%). Four (0.5%) patients had hypotension requiring vasopressors and 5 (0.6%) had the procedure terminated early. A total of 154 patients required one or more airway interventions, with 97 (12.1%) requiring a chin lift, 29 (3.6%) modified mask airway, and 28 (3.5%) nasal airway. No patient required bag valve mask ventilation or intubation. Independent predictors of need for airway intervention were BMI (odds ratio: 1.05, 95% CI 1.01-1.09), male gender (odds ratio: 1.75, 95% CI 1.08-2.85), and ASA ≥ 3 (1.90, 95% CI 1.11-3.25).

Conclusion            When propofol was administered by anesthesia professionals, the incidence of sedation-related adverse events was low.

 

Comment

The purpose of this study was to describe how often and what type of airway interventions were needed when propofol is administered by CRNAs with extensive experience in providing monitored anesthesia care for advanced endoscopy procedures. I think readers of this article should understand that the three CRNAs who provided sedation for these patients most likely do this on a full time basis in a center that probably performs the most advanced endoscopy procedures in the country, and is thus well equipped to provide the level of sedation required for these procedures. Therefore, I would be cautious in trying to generalize these results to other centers (i.e., smaller facilities) with anesthesia providers less experienced with these procedures, and certainly not to non-anesthesia providers (gastroenterologist-supervised RNs).

Additionally, 87.2% of patients had no response to endoscope insertion, which the authors categorized as deep sedation, when in fact the depth of sedation was really general anesthesia. This is not surprising, given the propofol induction dose was almost 1.8 mg/kg. In my experience this amount of propofol is not necessarily uncommon; however given the 14.4% of patients who needed one or more airway interventions, I think it is important that the person administering the propofol be able to recognize and treat airway obstruction in a patient in a less than optimal position (i.e., prone with endoscope in place). The authors of this study point out in their methods section at their facility the way they achieve this is by using CRNAs to administer propofol for advanced endoscopy procedures.

For these types of procedures I think it is essential that anesthesia providers have the proper equipment to monitor (e.g., end tidal CO2) and rescue patients (e.g., Jackson-Reese, nasal airways, ambu bag, anesthesia machine). In many institutions, especially those that do not do the same volume of cases as this facility, patients may be electively intubated to ensure a patent airway. In fact, a recent closed claims review of remote site anesthesia found that the GI suite had the most anesthesia associated claims (32%; 82% of cases MAC).1 Over sedation was identified in over half of the GI suite claims and more than half of these where associated with ERCPs and upper GI endoscopies. Therefore, in my opinion, I think unless anesthesia providers have a similar set-up as was described in this study, they should consider securing the airway (i.e., intubation) or perform the procedure in an operating room setting if there is any concern over the patient’s comorbidities or the anesthesia providers’ ability to safely administer the anesthetic in the GI clinic.

One major limitation of this study was that they did not measure, nor did they talk about, obstructive sleep apnea (OSA). OSA is probably one of the most common reasons anesthesia providers are consulted to provide sedation for advanced endoscopy procedures. I am amazed, given an anesthesiologist was a co-author on this study, that this issue was not addressed in the study design. Looking at the data, they had at least two risk factors for OSA: age over 50, and male gender. Additionally, a majority of the patients were ASA Class 3, and I suspect many had hypertension, which is another risk factor for OSA. I think if the authors had included these risk factors, the odds of needing airway interventions would have been greater than what they found. Finally, there is no way to tease out the effect of polypharmacy on the need for airway intervention from the data presented.

  

Dennis Spence, PhD, CRNA

 

 

1. Metzner J, Posner KL, Domino KB. The risk and safety of anesthesia at remote locations: the U.S. closed claims analysis. Curr Opin Anesthesiol 2009; 22: 502-508

 

 

Editor’s Note: See the following in previous issues of Anesthesia Abstracts for additional information on the risks sedation and the need for an anesthesia provider.

INJURY AND LIABILITY ASSOCIATED WITH MONITORED ANESTHESIA CARE in Anesthesia Abstracts · Volume 1 Number 1, March 30, 2007.

LEVELS OF CONSCIOUSNESS DURING REGIONAL ANESTHESIA AND MONITORED ANESTHESIA CARE: PATIENT EXPECTATIONS AND EXPERIENCES in Anesthesia Abstracts · Volume 3 Number 4, April 30, 2009.

 

The views expressed in this article are those of the author and do not reflect official policy or position of the Department of the Navy, Department of Defense or the United States Government.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010





Gras S, Servin F, Bendairia E, Montravers P, Desmonts J-M, Longrois D, Guglielminotti J


 

 

The effect of preoperative heart rate and anxiety on the propofol dose required for loss of consciousness

Anesth Analg 2010;110:89-93

Gras S, Servin F, Bendairia E, Montravers P, Desmonts J-M, Longrois D, Guglielminotti J

 

Abstract

Purpose            The primary purpose of this study was to examine the effect of heart rate (HR) on the dose of propofol required to produce loss of consciousness. The secondary purpose was to examine the effect of preoperative anxiety on HR.

Background            There is evidence that the more anxious the patient, the greater dose of induction drug needed to produce general anesthesia. Cardiovascular variables, such as HR, cardiac output (CO), and blood pressure (BP) may affect the dose of propofol needed for induction. Similarly, anxiety is associated with increased HR and cardiac output; thus changes in HR may affect the dose of induction drug needed to produce anesthesia. Other factors affect HR, including dehydration which may be present in surgical patients.

Methodology            This prospective, blinded study included 18 year old to 65 year old, ASA I and II, patients undergoing elective gynecologic surgery. Women with neurologic or psychiatric disease; chronic medication with ß-blockers, anxiolytics, antidepressants, or opioids; or substance abuse were excluded from the study.

Anxiety was assessed with the previously validated State Trait Anxiety Inventory (STAI). STAI scores range between 20 and 80 with higher scores indicating greater anxiety. Patients did not receive any preanesthetic medication. In the OR the STAI assessment was completed and vital signs were recorded. Anesthesia was then induced with a propofol infusion delivered at a rate of 33.3 mg/min, a dose per minute that would require 6 minutes to deliver 200 mg. Loss of consciousness was assessed by a single investigator every 15 seconds by asking the patient in a normal tone of voice to state her name. The investigator assessing loss of consciousness was blinded to the results of the STAI assessment.

Statistical analysis was appropriately conservative.

Result            STAI anxiety scores ranged from 20 to 60 with a median of 42. Patient weight ranged from 47 kg to 100 kg. There was a moderate correlation (ρ = 0.462) between the STAI anxiety state and HR which was not statistically significant. There was a moderate correlation (ρ = 0.487) between HR and propofol dose that was statistically significant. Correlation between BP and STAI anxiety state was poor. Multiple regression analysis showed that only HR at the time of induction predicted the dose of propofol required for loss of consciousness.

Conclusion            Higher heart rates were associated with the need for a greater dose of propofol to produce loss of consciousness. Situational anxiety is probably one cause of such higher heart rates. The proper dose of propofol for induction of anesthesia should be determined by individual titration.

 

Comment

This was a hard study to do and these investigators did a pretty good job. The investigators were right to use a nonparametric correlation (Spearman) to assess the relationship between the STAI anxiety score and vital signs. Many would have mistakenly used the parametric Pearson test. I really appreciated the fact that they looked not only at the correlation but also at the significance level (P value) for the correlation.

That said, I think they got a little too technical in their analysis and conclusions. I was left with the impression that the authors saw the association between HR and propofol dose as pretty strong and the relationship between STAI anxiety score and propofol dose as insignificant. My interpretation is slightly different. The association they found between HR and propofol dose and between STAI anxiety score and propofol dose are really just not all that much different.

I have to wonder if the results wouldn’t have been more convincing if the investigators had recorded the propofol dose in mg/kg rather than just mg. There was a fair amount of variability in patient weights, from 47 to 100 kg. It is almost a certainty that the unaccounted for differences in patient weight reduced the accuracy of the associations.

So where does all this leave us? This study, and other evidence, gives us a fairly good reason to think our patient's anxiety level and HR affect the dose of propofol needed to induce general anesthesia. While I’m not going to choose my initial induction dose based upon the patient’s heart rate, I do have yet another reason to do my best to make sure my patients are as relaxed as possible. That extra minute to develop a calming rapport may make induction easier for them and for you.

 

Michael Fiedler, PhD, CRNA

 

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010




Policy, Process, & Economics

Ishikawa Y, Kiyama T, Haga Y, Ishikawa M, Takeuchi H, Kimura O, Harihara Y, Sunouchi K, Furuya T, Kimura M


Maximal sterile barrier precautions do not reduce catheter-related blood stream infections in general surgery units

Ann Surg 2010;251:620-623

Ishikawa Y, Kiyama T, Haga Y, Ishikawa M, Takeuchi H, Kimura O, Harihara Y, Sunouchi K, Furuya T, Kimura M

Abstract

Purpose            The purpose of this study was to examine the effectiveness of maximal sterile barrier precautions (MSBPs) during the insertion of central venous catheters on the resulting incidence of catheter related infections in general surgical patients.

Background            Maximal sterile barrier precautions for central venous catheter insertion include the use of a large sterile sheet draping while the provider wears cap, mask, sterile gown and sterile gloves. The Centers for Disease Control and Prevention (CDC) issued guidelines in 2002 recommending that providers use MSBPs when inserting central venous catheters. MSBPs have been associated with reduced catheter related infection in chemotherapy outpatients and intensive care unit (ICU) inpatients, but the population of general surgery patients has not been studied.

Methodology            This prospective study was conducted in 9 clinical centers in Japan. Non-ICU surgical patients who were scheduled for central venous catheter insertion were randomly assigned to one of two groups. The treatment group had their catheters inserted under MSBP conditions. Catheters in the control group were inserted using standard precautions of sterile gloves and a small drape. Patients with elevated temperatures, those receiving antibiotics, or whose insertion was for replacement of an existing catheter were excluded from the study. Physicians inserted all catheters, but no description is provided of their specialization or level of experience. Both groups were managed the same, other than the difference in barrier precautions. Provider hand hygiene and patient skin preparation were standardized. Both groups received the same transparent dressings which were changed weekly. Infusion lines were replaced every 72 hours and after every administration of fat emulsion preparations or blood products.

Patients were observed for eight weeks, or until the catheter was removed. Blood cultures were obtained for any suspected infection related to the catheter. Laboratory personnel evaluating the blood culture results were blinded to patient group assignment.

Result            The treatment and control groups were similar in demographic characteristics, primary underlying disease, reason for insertion, most common site of insertion, most common type of catheter, catheterization duration, and complication rates. Sixty two patients had suspected infection, but some showed no sign of bloodstream infection, or a source other than the catheter was identified. There were 8 cases of catheter related infection in the treatment group and 7 in the control group. There were 5 cases of catheter related bloodstream infection in the treatment group and 6 in the control group. The rate of catheter related bloodstream infection per 1,000 days was 1.5 in the treatment group and 1.6 in the control group. None of these differences were statistically significant at a P value of 0.05.

Conclusion            This study failed to demonstrate a reduction in catheter related bloodstream infections for general surgical patients whose central venous catheters were inserted using MSBPs. While this statistical analysis yielded negative results, the possibility of a false negative remains. A false negative occurs when an actual difference does exits between the two groups, but the study fails to demonstrate the difference. The likelihood of a false negative is described by a power analysis. The power analysis offered by these authors indicates that this study’s methodology does include a false negative risk that should be considered when interpreting these results. Each of the two groups in this study included about 200 patients. In order to reduce the chance of a false negative to an acceptable level of 10-20%, each of the groups in this study would have needed 400 - 500 patients.

Comment

Recent health policy initiatives have put a spotlight on central venous catheter infections. Traditional reimbursement patterns of fee for service are being replaced with those grounded in pay for performance. One of the early examples of this paradigm shift is the decision of the Center for Medicare and Medicaid services to not cover the costs associated with hospital acquired infections including those of central venous catheters. The Joint Commission requires that hospitals implement policies aimed at the reduction of central venous catheter infections. In response to these financial and accreditation pressures, many hospitals have adopted the 2002 CDC guidelines requiring MSBPs during the insertion of central venous catheters. MSBP policies affect health care providers responsible for the insertion of these catheters, including nurse anesthetists. In addition to the possible increased time commitment related to compliance, departments incur additional costs associated with the supplies required for MSBPs. Such additional costs are well justified if they result in the benefit of fewer catheter infections.

This study examined an important question. What is the evidence that MSBP will make a difference on the incidence of central venous catheter infections in general surgical patients? Current CDC guidelines were developed based on studies involving patients receiving chemotherapy. Subsequent studies in ICU patients confirmed the beneficial affect of MSBPs. Many routine surgical patients who receive a central venous catheter may not be as immuno-compromised as the patients in those studies and not be as vulnerable to infection. While universal adoption of MSBPs may result in appropriate care for some patients, blanket application may actually be excessive for others. Consequently, it is possible that some providers and departments are paying costs for which their patients are not receiving significant benefit. Departments that value standardization may be comfortable with such a one-size-fits-all policy. Departments choosing to customize their procedures could benefit from knowledge that their catheter insertion practices are grounded in evidence that can be reasonably generalized to a particular individual patient. Studies such as this one, involving general surgical patients, contribute to our ability to develop these individualized best practices.

Unfortunately, methodological concerns limit the usefulness of this study in making decisions regarding the appropriateness of MSBP in general surgical patients. In the evaluation of health care research, we are often concerned with the possibility of a false positive. We use research results to justify making one treatment choice over another. With adequate control, we can be reasonably sure that the difference between the two actions in fact exists, and is not a false positive. Researchers control for the likelihood of a false positive by selecting an appropriate P value, often 0.05. In a study such as this one, we are concerned about the possibility of a false negative. In order to use this study as evidence that MSBPs are not necessary in general surgical patients, we need to be sure that in fact no difference exists between the two study groups and that the result is not a false negative. An acceptable likelihood of a false negative is often set at 10-20%, and can be determined through a statistical power analysis. This study’s sample size was too small to achieve this degree of power. Consequently, we cannot be confident that their result is not a false negative.

This study illustrated why it is ideal to perform a power analysis early in the design of a research study, in order to insure appropriate sample size. Due to some extenuating circumstances, these authors did not achieve enough power in their design to make their results meaningful. However, they did raise an important question that merits further investigation. Undoubtedly their study will be replicated with a bigger sample. The results of such a study will be noteworthy to nurse anesthetists and other health care providers involved with the insertion of central venous catheters in surgical patients.

 

Cassandra Taylor, DNP, DMP, CRNA, CNE

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010




Quality Improvement

Lehmann M, Monte K, Barach P, Kindler CH


 

 

Postoperative patient complaints: a prospective interview study of 12,276 patients

J Clin Anesth 2010;22:13-21

Lehmann M, Monte K, Barach P, Kindler CH

 

 

Abstract

Purpose            The purposes of this study were to determine the incidence of minor adverse events associated with anesthesia and to correlate patient satisfaction with minor anesthesia adverse events.

Background            The incidence of severe injury and death associated with anesthesia is quite low. Little, however, is known about the incidence, discomfort experienced, and patient perception associated with minor adverse events common to anesthesia. Adverse events in anesthesia are likely underreported. Overall patient satisfaction ratings are of limited value if one wants to learn about satisfaction with anesthesia care. Previous studies have reported the incidence of severe Postoperative Nausea and Vomiting (PONV) to be 10% and moderate to severe postoperative pain to be 24%. A strong relationship has been shown between PONV, pain, and patient dissatisfaction.

Methodology            This prospective, observational study included all types of surgical patients whose procedure was performed at a single institution between January 2003 and June 2006. Every fourth patient participated in a structured interview between the second and fifth postoperative days. Interviews were performed by five nurses who had been trained by a psychologist in “qualitative narrative methods” and structured interview techniques. Written guidelines were followed. Interrater reliability between the five interviewers was established in a test group of 128 patients. There were no significant differences between interview results. Interviews of inpatients were face to face. If the patient had been discharged, interviews were conducted over the telephone. Patient satisfaction was coded as either, not satisfied, moderately satisfied, satisfied, or highly satisfied.

Result            The study included 12,276 patients; 47% men and 53% women. Their average age was 53.4 years old ± 18.2 years. Anesthesia type was: 60.6% general only, 34.5% regional only, and 4.9% combined regional and general anesthesia. ASA physical status ranged from I to IV, with 70% being ASA II or less.

Anesthesia related complaints were expressed by 30% of study patients (3,652). One or more minor complications were reported by 38% (2,854) of patients who underwent general anesthesia and 14% (600) of patients who underwent only regional anesthesia. Two or more minor complications were reported by 8.5% (635) of patients who underwent general anesthesia and 1.5% (63) of patients who underwent only regional anesthesia.

 

 

Table 1:           Most Common Anesthesia Related Complaints

Number of Complaints

PONV

1,705

Sore Throat

1,228

Hoarseness

802

Injury to Lips / Mouth

260

Uncomfortable IV placement

206

Urinary Retention

142

Back Pain

120

Postoperative Delirium

100

Intraoperative Awareness

9

 

PONV was reported more often by young, female patients with a low ASA physical status classification and by cardiothoracic patients. Sore throat and hoarseness was reported significantly more by women than by men. Of those with postoperative sore throat, 75% underwent routine endotracheal intubation without any documented injury. The remaining 25%: had a TEE probe inserted (10%), an LMA was used (6%), had a difficult intubation (6%), or were intubated with a fiberoptic bronchoscope (3%). Back pain was reported most often by younger patients who underwent regional or combined regional and general anesthesia. Lip and mouth injury were associated with general anesthesia. Delirium occurred almost exclusively following general anesthesia; most had “poor medical status” prior to receiving an anesthetic and 81% were over age 65 years. Of those with delirium postoperatively, 41% had cardiac surgery. Nerve lesions were reported by 2 patients following regional anesthesia, 16 patients who received general anesthesia, and 6 patients following a combined regional / general anesthetic. Awareness was reported by 0.07% of patients who received a general anesthetic.

Patient satisfaction was significantly higher following regional than following general anesthesia (P=0.006). Overall patient satisfaction was high with 97.4% reporting having been either “highly satisfied” or “satisfied.” Only 1.4% were “moderately satisfied” and 1.2% were “dissatisfied with anesthetic care. Patient dissatisfaction was associated with having experienced one or more adverse events (P<0.001).

Conclusion            Overall satisfaction with anesthesia care is high but minor adverse events are common and strongly associated with patient dissatisfaction. Minor adverse events should be more aggressively tracked and anesthesia providers made aware of the incidences of these complications.

 

Comment

As the investigators pointed out, few studies have examined the incidences of “minor” adverse events in anesthesia. While our primary attention should continue to be focused upon preventing significant morbidity and mortality, there is no reason we can’t pay attention to “minor” adverse events at the same time. These minor adverse events play a large role in determining whether or not a patient will be satisfied with their anesthesia experience. And, as health care becomes more consumer oriented, patient satisfaction is playing a larger and larger role in where patients go for their care and who the institution contracts with to provide it.

The use of a structured interview by trained interviewers makes this study stronger than most others that have used crude survey forms. It is because this was a pretty well executed study that we should pay careful attention to what it has to teach us. For example, I don’t think anyone knows what the overall average of patient anesthetic complaints is but I bet most of us would be surprised to learn that it was 30% as reported in this study. If 30% of my patients have a complaint about anesthesia I’m hoping the complaint rate is even higher at the other hospitals in town and thinking about ways to get that complaint rate down.

The study validated what we probably already knew, that the biggest cause of patient complaints is PONV. The problem here is that even though we have multiple sources of evidence telling us that PONV is the most common anesthesia related complaint we don’t do what we know to do to reduce the rate of PONV. Study after study has shown that we do not routinely assess the risk of PONV before the case. Even something as quick as the Simplified PONV Risk Scale (1), which predicts PONV risk pretty well, isn’t regularly used preoperatively. Then, when we do identify a patient at high risk for PONV we don’t plan for multimodal PONV prophylaxis. So, really, it is our own fault when patients complain about it.

Another lesson this study has for us concerns regional anesthesia. Now I understand that not everyone has mastered the performance of every regional block. But many of us do a number of blocks well, yet don’t use them because they take too long or the surgeon would rather have a general or one of any number of other pseudo-reasons. The message here is simple, patients are more satisfied with regional anesthesia. And we know that regional has a number of benefits for patient care and outcomes as well. Even more interesting, this and other studies, clearly show that the incidence of temporary and permanent nerve injury is higher following general anesthesia than following regional anesthesia. Yet, most anesthesia providers talk to patients about nerve injury preoperatively if they are planning a regional and don’t talk about nerve injury if they are planning a general anesthetic.(2, 3)

We can markedly improve the satisfaction of our patients with their anesthetic experience. All we need to do to get started is track their satisfaction and apply the evidence we already have available about how to address the minor adverse events that lead to their complaints.

 

Michael Fiedler, PhD, CRNA

 

1. Apfel et al. A simplified risk score for predicting postoperative nausea and vomiting: conclusions from cross-validations between two centers. Anesthesiology 1999;91:693-700.

2. Kroll DA, Caplan RA, Posner K, Ward RJ, Cheney FW. Nerve injury associated with anesthesia. Anesthesiology. 1990;73:202-207.

3. Brull et al. Disclosure of risks associated with regional anesthesia: a survey of academic regional anesthesiologists. Reg Anesth Pain Med 2007;32:7-11.

 

© Copyright 2010 Anesthesia Abstracts · Volume 4 Number 4, April 30, 2010